There are known problems with Perl6::Rules under perl 5.8.4 and later. I.e. some features of the module don't work properly any more. Since Perl6::Rules came out (and worked) under 5.8.3, the valiant Perl 5 porters have started fixing some very deep problems that the module had exposed in the core regex engine, specifically problems in the way that closures embedded in regexes (don't) work.

The regex engine has been a moving target since then, and probably will be for some time yet, so I've held off reworking Perl6::Rules until I can genuinely fix it.